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United States Patent |
5,254,408
|
Takeuchi
,   et al.
|
October 19, 1993
|
Magnet wire and electromagnetic relay using the same
Abstract
A polyurethane magnet wire comprising a conductor having provided thereon a
polyurethane insulation coating, wherein the total amount of the phenolic
compounds contained in organic compounds which evaporate from said coating
by heating at 280.degree. C. for 2 minutes is 0.2 wt % or less based on
the weight of the coating and the total amount of the organic compounds is
2 wt % or less based on the weight of the coating; and an electric relay
comprising such a wire.
Inventors:
|
Takeuchi; Akihisa (Aichi, JP);
Kozen; Waichiro (Aichi, JP);
Nakabayashi; Hirohiko (Aichi, JP)
|
Assignee:
|
Sumito Electric Industrial Co., Ltd. (Osaka, JP)
|
Appl. No.:
|
117607 |
Filed:
|
November 6, 1987 |
Foreign Application Priority Data
| Nov 11, 1986[JP] | 61-268904 |
| Nov 11, 1986[JP] | 61-268905 |
| Nov 11, 1986[JP] | 61-268906 |
Current U.S. Class: |
428/383; 174/110SR; 174/120C; 174/120R; 174/120SR; 428/379; 428/380 |
Intern'l Class: |
B32B 027/00; D02G 003/00 |
Field of Search: |
428/380,379,383
174/120 SR,120 R,120 C,110 SR
|
References Cited
U.S. Patent Documents
3413148 | Nov., 1968 | Sattler et al. | 428/457.
|
3775175 | Nov., 1973 | Merian | 428/379.
|
4605917 | Aug., 1986 | Ide et al. | 428/383.
|
4716079 | Dec., 1987 | Sano et al. | 427/383.
|
Foreign Patent Documents |
0103307 | Mar., 1984 | EP.
| |
1248200 | Sep., 1971 | GB.
| |
Primary Examiner: Ryan; Patrick J.
Assistant Examiner: Coray; J. M.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas
Claims
What is claimed is:
1. A polyurethane magnet wire comprising a conductor having provided
thereon a polyurethane insulation coating, wherein the total amount of the
phenolic compounds contained in organic compounds which evaporate from
said coating by heating at 280.degree. C. for 2 minutes is 0.2 wt % or
less based on the weight of said coating, and the total amount of said
organic compounds which evaporate from said coating is 2 wt % or less
based on the weight of said coating.
2. A polyurethane magnet wire as claimed in claim 1, wherein the total
amount of said phenolic compounds is 0.1 wt % or less based on the weight
of said coating.
3. A polyurethane magnet wire as claimed in claim 1, wherein the total
amount of said organic compounds is 1 wt % or less based on the weight of
said coating.
4. A polyurethane magnet wire as claimed in claim 1, wherein the total
amount of said phenolic compounds is 0.1 wt % or less based on the weight
of said coating and the total amount of said organic compounds is 1 wt %
or less based on the weight of said coating.
5. A polyurethane magnet wire comprising a conductor having provided
thereon a polyurethane insulation coating, wherein the total amount of the
phenolic compounds contained in organic compounds which evaporate from
said coating by heating at 280.degree. C. for 2 minutes is 0.2 wt % or
less based on the weight of said coating, and the total amount of said
organic compounds is 2 wt % or less based on the weight of said coating,
and having provided on said polyurethane insulation coating a coating of
an organic lubricant having a vapor pressure of 1.times.10.sup.-1 Torr or
less at 200.degree. C.
6. A polyurethane magnet wire as claimed in claim 5, wherein the total
amount of said phenolic compounds is 0.1 wt % or less based on the weight
of said coating.
7. A polyurethane magnet wire as claimed in claim 5, wherein the total
amount of said organic compounds is 1 wt % or less based on the weight of
said coating.
8. A polyurethane magnet wire as claimed in claim 5, wherein the total
amount of said phenolic compounds is 0.1 wt % or less based on the weight
of said coating and the total amount of the said organic compounds is 1 wt
% or less based on the weight of said coating.
9. A polyurethane magnet wire as claimed in claim 5, wherein said organic
lubricant is a polyolefinic hydrocarbon.
10. A polyurethane magnet wire as claimed in claim 9, wherein said
polyolefinic hydrocarbon is polyethylene, polypropylene, or
polymethylpentene.
11. A polyurethane magnet wire as claimed in claim 5, wherein the coating
of an organic lubricant is formed by applying and baking an enamel
comprising (a) polyethylene, (b) a binder for preventing the separation of
a polyethylene coat, and (c) a solvent.
12. A polyurethane magnet wire as claimed in claim 11, wherein the weight
ratio of said polyethylene (a) to said binder (b) is in the range of from
1/99 to 90/10.
13. A polyurethane magnet wire as claimed in claim 11, wherein the weight
ratio of said polyethylene (a) to said binder (b) is in the range of from
10/90 to 50/50.
14. A polyurethane magnet wire as claimed in claim 11, wherein said
polyethylene (a) has an average molecular weight of 5,000 or less.
15. A polyurethane magnet wire as claimed in claim 11, wherein said
polyethylene (a) has an average molecular weight of 500 or more.
16. A polyurethane magnet wire as claimed in claim 11, wherein said binder
(b) is a resin.
17. A polyurethane magnet wire as claimed in claim 11, wherein said binder
(b) is a thermoplastic resin.
18. A polyurethane magnet wire as claimed in claim 11, wherein said binder
(b) is a thermosetting resin.
19. A polyurethane magnet wire as claimed in claim 11, wherein said binder
(b) is a resin that is useful as an insulation enamel of magnet wire.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a magnet wire used in excitation coils in
electrical equipment such as an electromagnetic relay, as well as to an
electromagnetic relay using this magnet wire. In particular, the present
invention relates to a magnet wire for use in a sealed type
electromagnetic relay which has both relay contacts and drive coils
confined and sealed in a common space. The present invention also relates
to a sealed type electromagnetic relay using such a magnet wire.
Magnet wires of the type contemplated by the present invention are
conventionally produced by the following procedures: a enamel of an
electrically insulating material dissolved in an organic solvent is
applied to the circumference of a conductor such as a copper wire and
subsequently cured with heat to form an insulation coating, which is then
coated with a layer of a lubricant such as paraffin or oil so as to
provide good slipping property of the magnet wire and to prevent it from
breaking during winding. Polyurethane based compounds are commonly used as
the electrically insulating materials of the enamel. A cross section of
the so prepared magnet wire is shown in FIG. 1, in which 1 is a conductor
2 is an insulation coating, and 3 is a layer of lubricant.
A sealed type electromagnetic relay using excitation coils which are formed
of the magnet wire of the type described above is shown schematically in
FIG. 2, in which the excitation coils are indicated by 4. As the relay is
repeatedly operated, the lubricant component in the coils evaporate to
generate a gas which fills the space in a closed vessel 5 and is deposited
or carbonized by arc on the surface of contact elements 6 as it is
cyclically brought into an open and a closed position. This deposition or
carbonization of the evaporated lubricant component inevitably increases
the contact resistance of the contact elements. In addition, the remaining
solvent in the insulation coating of the coils 4, the unreacted phenolic
compound used as a masking agent for the masked polyisocyanate which is
one of the starting materials for the production of the polyurethane
resin, and a low molecular weight organic compound such as the thermal
decomposition product of the insulation coating which forms as a result of
baking with heat, evaporate to generate a gas which fills the space in the
vessel 5 and is carbonized on the surface of the contact elements 6 as it
is cyclically brought into an open and a closed position, thereby
increasing the contact resistance of the contact elements. In either case,
the reliability of the sealed type electromagnetic relay is reduced.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a magnetic
wire which is free from the aforementioned problems encountered in the
conventional electromagnetic relay employing excitation coils.
Other and further objects of the present invention will appear more fully
from the following description.
As a result of various studies conducted in order to solve the
aforementioned problems, the present inventors found that the above and
other objects of the present invention can be attained by a polyurethane
magnet wire comprising a conductor having provided thereon a polyurethane
insulation coating, wherein the total amount of the phenolic compounds
contained in organic compounds which evaporate from the coating by heating
at 280.degree. C. for 2 minutes is 0.2 wt % or less based on the weight of
the coating, and the total amount of the organic compounds is 2 wt % or
less based on the weight of the coating; and an electromagnetic relay
comprising such a wire. The present invention has been accomplished on the
basis of this finding.
The present inventors also found that the objects can be attained more
effectively by a polyurethane magnet wire comprising a conductor having
provided thereon a polyurethane insulation coating, wherein the total
amount of the phenolic compounds contained in organic compounds which
evaporate from the coating by heating at 280.degree. C. for 2 minutes is
0.2 wt % or less based on the weight of the coating, and the total amount
of the organic compounds is 2 wt % or less based on the weight of the
coating and having provided on the polyurethane insulation coating a
coating of an organic lubricant having a vapor pressure of
1.times.10.sup.-1 Torr or less at 200.degree. C.; and an electromagnetic
relay comprising such a polyurethane magnet wire. The present invention
has been accomplished on the basis of this additional finding.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross section of a magnet wire;
FIG. 2 is a schematic diagram of an electro-magnetic relay which is one
example of the applications of the magnet wire; and
FIG. 3 is a schematic diagram of an experimental apparatus used to evaluate
the performance of the magnet wires prepared in Examples 1 to 21 of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
The polyurethane enamel used in the present invention to make the
polyurethane insulation coating is prepared by dissolving in a solvent a
compound having active hydrogen in the molecule and a polyisocyanate
compound or a masked polyisocyanate compound. The polyurethane enamel may
also contain an additive such as a lubricant, a pigment, a dye, a curing
agent, a filler, etc.
The organic lubricant which can be used in the present invention and which
has a vapor pressure of 1.times.10.sup.-1 Torr or less at 200.degree. C.
is preferably selected from among polyolefinic hydrocarbon compounds
because of their good lubricating property, and polyethylene,
polypropylene, and polymethylpentene are particularly preferred. These
polymers may be straight-chain or branched in their backbone structure.
From the viewpoint of lubricating efficiency, a straight-chain
polyethylene is most preferred.
Another preferred coating of organic lubricant may be formed by applying
and baking an enamel which comprises (a) polyethylene, (b) a binder for
preventing separation of a polyethylene coat, and (c) a solvent. The
weight ratio of (a) polyethylene to (b) binder is preferably in the range
of from 1/99 to 90/10. If the weight ratio of (a) to (b) is less than
1/99, the lubricating property is relatively not excellent and if the
weight ratio of (a) to (b) is more than 90/10, the polyethylene coating
tends to separate. The weight ratio of (a) to (b) is more preferably in
the range of from 10/90 to 50/50 in view of a high lubricating effect
without causing separation of the lubricant coating.
The average molecular weight of the polyethylene (a) is preferably 5,000 or
less, and is preferably 500 or more. If a polyethylene having an average
molecular weight of more than 5,000 is used, a smooth lubricant coat will
not be formed on the surface of a magnet wire and the commercial value
will relatively be impaired. A polyethylene having an average molecular
weight of less than 500 tends to evaporate upon heating and is not
preferred for forming a satisfactory film of lubricant. However, even if
the average molecular weight of the polyethylene is more than 5,000 or
less than 500, the above disadvantage is arisen, but the effects of the
present invention are maintained.
Any resin can be used as the binder (b) for preventing the separation of
polyethylene coating so long as it is capable of preventing separation of
a polyethylene coating after it has been applied to the magnet wire and
subsequently baked with heat. A preferred binder resin include a
thermoplastic resin or a thermosetting resin which, when baked, undergoes
crosslinking of the molecules to form a macromolecule. Also usable is a
resin which is conventionally incorporated in an insulating enamel for
making a magnet wire.
The amounts of the organic compounds which are evaporated from the
insulation coating of the magnet wire can be determined by the following
procedure.
First, the coating is heated to 280.degree. C. for 2 minutes and the
evaporating gases are analyzed with an appropriate apparatus such as a gas
chromatograph or a mass spectrometer, followed by determining the
quantities of each of the organic compounds with a suitable instrument
such as an integrator attached to the analyzer.
More specifically, the present inventors employed the following method. A
sample of approximately 20 mg of the magnet wire was accurately weighed
and a gas chromatograph (Model 163 of Hitachi, Ltd.) was directly coupled
to a heat decomposition furnace (Model KP-1 of Hitachi, Ltd.) in which the
sample was set and heated at 280.degree. C.
The organic compounds which evaporated from the insulation coating of the
sample were introduced together with a carrier gas (high-purity N.sub.2
gas), into a separation column of 1 m length which was installed on the
gas chromatography.
The sample was recovered from the heat decomposition furnace two minutes
after it was charged into the furnace. The organic compounds separated by
the column were detected with an H.sub.2 flame ionizing detector and the
detected signals were counted with an integrator (Model 5000E of System
Instruments, Inc.).
Then the resulting counts were compared with those preliminarily obtained
from a standard solution of each of the organic compounds to determine the
quantities of the evaporated organic compounds.
Finally, the weight percentages of the evaporated organic compounds were
calculated from the weight of the insulation coating as determined from
the weight of the sample.
The present inventors used an experimental apparatus of the type shown in
FIG. 3 in order to investigate what effects the organic compounds
evaporated from the insulation coating on a magnet wire or from the
surrounding lubricant coating would have on the contact resistance of the
electrical contact elements in an electromagnetic relay.
Referring to FIG. 3, a sample wire 7, is heated to evaporate a gas which
fills a closed vessel 8 and which is carbonized on the surface of an
electrical contact element 10 which is cyclically brought to an open or a
closed position by means of coils 9. The resulting increase in the contact
resistance of the contact element 10 is measured with a 4-terminal contact
resistance meter 11. The effect of the sample wire 7 on the contact member
can be identified by counting the number of times that the contact can be
cyclically brought to open and closed positions before the measured
contact resistance exceeds a certain value.
Experimental measurement with the apparatus shown in FIG. 3 was conducted
in an atmosphere held at 120.degree. C.
The present inventors conducted similar experiments for various types of
lubricants and magnet wires with a polyurethane coating.
As a result of the tests described above, the present inventors found that
the increase in the contact resistance of the contact element in an
electromagnetic relay correlates to the vapor pressure of the lubricant
and to the amounts of phenolic compounds evaporating from the insulation
coating of the magnet wire. The total amount of the evaporating organic
compounds is also a factor which influences the contact resistance of the
contact element. The amount of evaporation is evaluated by that from the
insulation coating per unit weight.
Phenolic compounds are commonly used as solvents for polyurethane enamels.
They are also used as masking agents for the masked polyisocyanate, which
is one of the starting materials for the manufacture of polyurethane.
Other volatile organic compounds are generated when enamel solvents other
than phenolic compound and the material of which the polyurethane coating
is formed are thermally decomposed by baking.
Of the volatile organic compounds mentioned above, the evaporation of
phenolic compounds decreases, if the applied polyurethane coating is
adequately baked.
This is also true for other enamel solvents.
However, the thermal decomposition products of the polyurethane coating
increase the more the polyurethane coat is baked.
Therefore, in order to decrease both the amount of phenolic compounds that
are evaporated from the insulation coating of the magnet wire and the
total amount of volatile organic compounds, the degree of baking of the
enamel coating applied to a magnet wire must be properly controlled.
Some commercial polyurethane enamels are of such a nature that if their
coats are baked under the conditions that reduce the evaporation of
phenolic compounds to below a certain level, thermal decomposition of the
insulation coating already has occurred to a substantial extent and cannot
be suppressed to a level below a certain value. Magnet wires which are
insulated with such enamels are not suitable for use in excitation coils
in an electromagnetic relay no matter what conditions are employed to bake
the insulation coating.
Therefore, in order to make a magnet wire with a polyurethane based coating
that is suitable for the purposes of the present invention, it is
necessary not only to control the degree of baking of the insulation
enamel applied to a magnet wire, but also to employ an appropriately
selected insulation enamel.
A specific polyurethane based insulation enamel which was appropriately
selected was applied to a conductor and subsequently baked with heat under
certain conditions.
The resulting magnet wire was tested with an apparatus of the type shown in
FIG. 3 in order to examine the effects of volatile gases on the contact
resistance of a contact element.
It was found that if the total amount of phenolic compounds present in the
organic compounds evaporated from the insulation coating is 0.2 wt % or
less of the coating and if the total amount of the evaporated organic
compounds is 2 wt % or less of the coating, the contact element can be
cyclically brought to open and closed positions at least 5.times.10.sup.6
times before the increase in the contact resistance of the contact element
exceeds a critical value. A rating of 5.times.10.sup.6 times that the
contact element can be repeatedly brought to open and closed positions is
often considered to be a minimum figure for a commercially acceptable
electromagnetic relay.
More favorable conditions are attained if the total amount of phenolic
compounds evaporated from the insulation coat is reduced to 0.1 wt % or
less and below of the coating, and the total amount of the evaporated
organic compounds is reduced to 1 wt % or less of the coating. Under such
conditions, the contact element can be cyclically brought to open and
closed positions at least 1.times.10.sup.7 times before the increase in
the contact resistance of the contact element exceeds a critical value.
Obviously, the magnet wire of the present invention is markedly improved
over the prior art product which permits the contact element to be
cyclically brought to open and closed positions only about
3.times.10.sup.6 times under the same testing conditions.
The present inventors also conducted an experiment to investigate the
effect of the organic lubricant coated on the polyurethane magnet wire. To
this end, various organic lubricants were compared for their effect on the
increase in the contact resistance of the contact element in an
electromagnetic relay employing the magnet wire in excitation coils. As a
result, it was found that the vapor pressure of the organic lubricant is a
significant factor in that no organic lubricant will cause adverse effects
on the contact element if it has a vapor pressure of 1.times.10.sup.-1
Torr or less at 200.degree. C.
The following examples and comparative examples are provided for the
purpose of further illustrating the present invention but are in no way to
be taken as limiting its scope.
Unless otherwise specified, all parts, percents, ratios, and the like are
by weight.
COMPARATIVE EXAMPLES 1 TO 5
Round copper wire having a conductor diameter of 50 .mu.m were provided
with 14 layers of a polyurethane insulation coating made by applying a
polyurethane based insulation enamel (TPU K5-101 of Totoku Paint Co.,
Ltd.) which was subsequently baked under different temperature conditions.
The coating speed of the magnet wire is 350 m/min.
Each of the magnet wires having different degrees of baking in the
insulation coat was charged into an electric furnace held at 280.degree.
C., and the evaporating organic compounds were supplied into a gas
chromatograph that was directly coupled to the electric furnace and which
was equipped with a hydrogen flame ionization detector. The organic
compounds were separated according to their type and their quantities were
determined with an integrator. The measurements are shown in Table 1.
Each of the magnet wires was also placed in the closed vessel of an
apparatus of the type shown in FIG. 3 and the time-dependent change in the
contact resistance of the contact elements was measured for each magnet
wire. Four contact elements were tested under the same conditions and the
number of times that they could be cyclically brought to open and closed
positions before the average of the contact resistance of the four contact
elements reached 100 milliohms was counted. Each of the contact elements
had an initial contact resistance of 20 milliohms. The resistance
measurements are also shown in Table 1.
TABLE 1
__________________________________________________________________________
Number of times
Amount of volatile
that contact elements
Baking temperature
organic compounds
could by cyclically operated
(furnace temperature)
Phenolic before contact resistance
Run No.
(.degree.C.)
compounds (%)
Total (%)
exceeded 100 m.OMEGA. (.times.10.sup.5)
__________________________________________________________________________
Comparative
360 3.20 8.4 5
Example 1
Comparative
400 0.57 4.6 18
Example 2
Comparative
430 0.18 2.8 30
Example 3
Comparative
460 0.11 5.6 12
Example 4
Comparative
500 0.03 10.2 5
Example 5
__________________________________________________________________________
As Table 1 shows, none of the magnet wires tested satisfied the
requirements that the total amount of phenolic compounds evaporated from
the insulation coating should be no more than 0.2 wt % of the coating and
that the total amount of the evaporated organic compounds should not
exceed 2 wt % of the coating. In neither of the comparative examples
discussed here, the contact elements could be cyclically brought to open
and closed positions by at least 5.times.10.sup.6 times, which was the
desired value for a commercially acceptable electromagnetic relay.
EXAMPLES 1 TO 7 AND COMPARATIVE EXAMPLES 6 TO 8
Using a polyurethane based insulation enamel (APU-2138K of Auto Chemical
Industries Co., Ltd.), magnet wires having different degrees of baking in
the insulation coat were obtained in the same manner as in Comparative
Examples 1 to 5.
The amounts of organic compounds evaporating from these magnet wires and
the effects of such compounds on contact elements were determined in the
same manner as in Comparative Examples 1 to 5. The measurements are shown
in Table 2.
TABLE 2
__________________________________________________________________________
Number of times
Amount of volatile
that contact elements
Baking temperature
organic compounds
could by cyclically operated
(furnace temperature)
Phenolic before contact resistance
Run No.
(.degree.C.)
compounds (%)
Total (%)
exceeded 100 m.OMEGA. (.times.10.sup.5)
__________________________________________________________________________
Comparative
360 5.00 10.3 5
Example 6
Comparative
390 0.35 3.6 35
Example 7
Example 1
410 0.20 1.8 52
Example 2
420 0.13 1.6 80
Example 3
430 0.11 0.9 >100
Example 4
440 0.10 0.8 >100
Example 5
450 0.08 0.7 >100
Example 6
460 0.04 1.1 >100
Example 7
480 0.02 1.6 80
Comparative
500 0.01 6.3 5
Example 8
__________________________________________________________________________
As is clear from Table 2, the contact resistances of the contact elements
that were used with the magnet wires from which phenolic compounds were
evaporated in a total amount exceeding 0.2 wt % of the insulation coating
reached the value of 100 milliohms before the contact elements were
cyclically brought to open and closed positions by 5.times.10.sup.6 times.
When the total amount of phenolic compounds evaporating from the
insulation coat was no more than 0.1 wt % of the coating, the contact
elements could be cyclically brought to open and closed positions by at
least 1.times.10.sup.7 times before their contact resistances reached 100
milliohms. The increase in the contact resistance of the contact elements
was also promoted when the total amount of organic compounds evaporating
from the insulation coating exceeded 2 wt % of the coating. A more
preferred value of the total amount of organic compounds evaporating from
the insulation coat is 1 wt % or less of the coating.
COMPARATIVE EXAMPLE 9
A copper conductor having a diameter of 50 .mu.m was coated with 14 layers
of a polyurethane coating made by applying a polyurethane based insulation
enamel (APU-2138K of Auto Chemical Industries Co., Ltd.), which was
subsequently baked at 450.degree. C. to make a magnet wire. A coating of
liquid paraffin having a vapor pressure of 0.4 Torr at 200.degree. C. was
applied to the surface of the magnet wire. Thereafter, a certain amount of
the wire was sampled and washed with n-hexane to extract the liquid
paraffin. Calculation of the paraffin deposit on the magnet wire was made
on the basis of the measurement of the amount of extracted liquid paraffin
and this showed that the wire had a paraffin coating in a thickness of
0.06 .mu.m.
The magnet wire with a liquid paraffin coating was placed in the closed
vessel of an apparatus of the type shown in FIG. 3 and the time-dependent
change in the contact resistance of the contact element was measured. Four
contact elements were tested under the same conditions and the number of
times that they could be cyclically brought to open and closed positions
before the average of contact resistance of the four contact elements
reached 100 milliohms was counted. Each of the contact elements had an
initial contact resistance of 20 milliohms. The resistance measurements
are shown in Table 3.
COMPARATIVE EXAMPLE 10
A magnet wire prepared as in Comparative Example 9 was coated with a layer
of spindle oil having a vapor pressure of 3 Torr at 200.degree. C. The
thickness of the spindle oil coat was measured in the same manner as in
Comparative Example 9 and found to be 0.05 .mu.m.
The effects of the magnet wire on contact elements were investigated in the
same manner as in Comparative Example 9 and the results are shown in Table
3.
COMPARATIVE EXAMPLE 11
A magnet wire prepared as in Comparative Example 9 was coated with an
n-hexane solution of solid paraffin (vapor pressure at 200.degree. C.: 0.4
Torr) and the coating was subsequently dried. The thickness of the
paraffin coating was found to be 0.03 .mu.m on a dry basis. The effects of
the magnet wire on contact elements were investigated in the same manner
as in Comparative Example 9 and the results are shown in Table 3.
EXAMPLE 8
Polyethylene having an average molecular weight of 2,000 and a vapor
pressure of 0.1 Torr or less at 200.degree. C. was dissolved in xylene
with heat. The resulting solution was applied to the surface of the magnet
wire, which was obtained as in Comparative Example 9. After drying, the
polyethylene coating was found to have a thickness of 0.1 .mu.m. The
effects of the magnet wire on contact elements were investigated in the
same manner as in Comparative Example 9 and the results are shown in Table
3.
EXAMPLE 9
Polyethylene having an average molecular weight of 3,000 and a vapor
pressure of 0.1 Torr or less at 200.degree. C. was dissolved in aromatic
naphtha with heat. The resulting solution was applied to the surface of
the magnet wire which was obtained as in Comparative Example 9. After
drying, the polyethylene coating was found to have a thickness of 0.1
.mu.m. The effects of the magnet wire on contact elements were
investigated in the same manner as in Comparative Example 9 and the
results are shown in Table 3.
EXAMPLE 10
Polypropylene having an average molecular weight of 3,000 and a vapor
pressure of 0.1 Torr or less at 200.degree. C. was dissolved in xylene
with heat. The resulting solution was applied to the surface of the magnet
wire which was obtained as in Comparative Example 9. After drying, the
polypropylene coating was found to have a thickness of 0.1 .mu.m. The
effects of the magnet wire on contact elements were investigated in the
same manner as in Comparative Example 9 and the results are shown in Table
3.
EXAMPLE 11
Polymethylpentene having an average molecular weight of 10,000 and a vapor
pressure of 0.1 Torr or less at 200.degree. C. was dissolved in
cyclohexane with heat. The resulting solution was applied to the surface
of the magnet wire which was obtained as in Comparative Example 9. After
drying, the polymethylpentene coating was found to have a thickness of 0.1
.mu.m. The effects of the magnet wire on contact elements were
investigated in the same manner as in Comparative Example 9 and the
results are shown in Table 3.
EXAMPLE 12
Polyethylene (average molecular weight: 2,000) of the same type as used in
Example 8, a xylene-soluble polyvinyl butyral resin, and MS-50 (trade name
of Nippon Polyurethane Industry Co., Ltd. for a masked polyisocyanate)
were mixed at a weight ratio of 10/50/40 and the mixture was dissolved in
xylene with heat. The resulting solution was applied to the surface of the
magnet wire which was obtained as in Comparative Example 9. After baking,
the three-component coating on the magnet wire was found to have a
thickness of 0.1 .mu.m. The effects of the magnet wire on contact elements
were investigated in the same manner as in Comparative Example 9 and the
results are shown in Table 3.
EXAMPLE 13
Polyethylene (average molecular weight: 3,000) of the same type as used in
Example 9 and polyurethane based insulation enamel (APU-2138K of Auto
Chemical Industries Co., Ltd.) were mixed at a weight ratio of 20/80 on a
solids (resin) basis and dissolved in a 5/5 mixture of cresol and aromatic
naphtha (boiling in the range of 145.degree. to 155.degree. C.) by
heating. The resulting solution was applied to the surface of the magnet
wire, which was obtained as in Comparative Example 9. After baking, the
two-component coating on the magnet wire was found to have a thickness of
0.1 .mu.m. The effects of the magnet wire on contact elements were
investigated in the same manner as in Comparative Example 9 and the
results are shown in Table 3.
EXAMPLE 14
Polyethylene (average molecular weight: 3,000) of the same type as used in
Example 9, Epikote #1009 (trade name of Shell International Chemicals
Corp. for an epoxy resin), and MS-50 (trade name of Nippon Polyurethane
Industry Co., Ltd. for a masked polyisocyanate) were mixed at a weight
ratio of 1/53/46 and dissolved in a 4/6 mixture of cresol and aromatic
naphtha by heating. The resulting solution was applied to the surface of a
magnet wire, which was obtained in the same manner as in Comparative
Example 9. After baking, the three-component coating on the magnet wire
was found to have a thickness of 0.1 .mu.m. The effects of the magnet wire
on contact elements were investigated in the same manner as in Comparative
Example 9 and the results are shown in Table 3.
EXAMPLES 15 TO 21
The same procedures as in Example 14 were repeated except that the weight
ratio of polyethylene (average molecular weight: 3,000) of the same type
as used in Example 9, Epikote #1009 and MS-50 was changed to 10/48/42,
20/42/38, 30/37/33, 40/32/28, 50/27/23, 70/16/14 and 90/5/5, and were
subsequently dissolved in a 4/6 mixture of cresol and aromatic naphtha by
heating. The resulting solutions were applied to the surface of the magnet
wires which were obtained as in Comparative Example 9. After baking, the
three-component coating on each of the magnet wires were found to have a
thickness of 0.1 .mu.m. The effects of the magnet wire on contact elements
were investigated in the same manner as in Comparative Example 9 and the
results are shown in Table 3.
TABLE 3
__________________________________________________________________________
Number of times that
contact elements could
Lubricating or-
Average
Vapor pressure
by cyclically operated
ganic compound in
molecular
at 200.degree. C.
before contact resistance
Run No.
outermost layer
weight
(Torr) exceeded 100 m.OMEGA. (.times.10.sup.5)
__________________________________________________________________________
Comparative
liquid paraffin
-- 0.4 20
Example 9
Comparative
spindle oil
-- 3 5
Example 10
Comparative
solid paraffin
-- 0.4 17
Example 11
Example 8
polyethylene
2,000 <0.1 >100
Example 9
polyethylene
3,000 <0.1 >100
Example 10
polypropylene
3,000 <0.1 >100
Example 11
polymethylpentene
10,000
<0.1 >100
Example 12
polyethylene,
2,000 <0.1 >100
PVB, MS-50
Example 13
polyethylene,
3,000 <0.1 >100
urethane enamel
Example 14
polyethylene,
3,000 <0.1 >100
Epikote, MS-50
Example 15
polyethylene,
3,000 <0.1 >100
Epikote, MS-50
Example 16
polyethylene,
3,000 <0.1 >100
Epikote, MS-50
Example 17
polyethylene,
3,000 <0.1 >100
Epikote, MS-50
Example 18
polyethylene,
3,000 <0.1 >100
Epikote, MS-50
Example 19
polyethylene,
3,000 <0.1 >100
Epikote, MS-50
Example 20
polyethylene,
3,000 <0.1 >100
Epikote, MS-50
Example 21
polyethylene,
3,000 <0.1 >100
Epikote, MS-50
__________________________________________________________________________
Note: In Examples 14 to 21, the ratio of polyethylene, Epikote, and MS50
was varied.
As is clear from the results shown in Table 3 above, the polyurethane
magnet wire according to the present invention, i.e., that having an
organic lubricant coating having a vapor pressure of 1.times.10.sup.-1
Torr or less at 200.degree. C. has excellent properties as a magnet wire
for an electromagnetic relay.
While the invention has been described in detail and with reference to
specific examples thereof, it will be apparent to one skilled in the art
that various changes and modifications can be made therein without
departing from the spirit and scope thereof.
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